attempt at some more day/night/dusk cycleing..
reinstate the half gradient
recalculate t based on the offset we chose

thanks to urraka from #reddit-gamedev for this whole thing.
the part that was giving the most trouble was handling everything after
24.00 (well, 23:59:59, but for all intents and purposes..).
incorporate minutes into day/night shader blending
rm dead shader code
add night sky renderer shader (needs implemented still)
fix shader fuckup, opengl 3.2 -> opengl 3.0. i think it should work

don't think i use anything from beyond 3.0
fix remnant of box2d, seems i missed a few.